As is generally known, modern aircraft designs employ various control and avionics systems, such as radar and "black boxes," to aid in the operation of the aircraft. These control and avionics systems are typically interconnected using a plurality of wires, wherein these wires provide means for electrical communication between the systems.
As is known in the art, current in an electrical circuit creates a field of force associated with motion of the electrical charge. This field of force includes electric and magnetic components and, consequently, contains a finite amount of electromagnetic energy. This field of force is typically called an electromagnetic field. The electromagnetic field generated by an electrical circuit can induce current in an adjacent electrical circuit, thereby introducing noise into the adjacent circuit. This phenomenon also occurs in wires interconnecting the electrical circuits.
In aeronautic and astronautic applications, thousands of wires are routed throughout the aircraft in very tight bundles. As can be appreciated, these wires are susceptible to electromagnetic fields created by avionics on the aircraft and those near the aircraft, such as microwave towers or radar. If left unprotected, these electromagnetic fields induce noise into the wiring of the aircraft, thereby degrading the native signal carried in each of the wires. Moreover, because of the length of the wires extending through the aircraft, these wires act as very efficient antennas for picking up interference external to the aircraft.
Attempts have been made to shield these wires from the electromagnetic fields and outside interference. Typically, sensitive circuits, those unable to tolerate noise created from electromagnetic fields, are made using individual wires that are shielded. During manufacture, strands of copper are first plated using either tin, nickel, or silver and are then woven in place over the insulated wire to form a braided shield. Additional insulation is then put over the braided shield to form a cable, which is resistant to electromagnetic fields. Unsensitive circuits, those able to tolerate limited amounts of noise created from electromagnetic fields, are made according to conventional wire making methods.
During wiring of an aircraft, sensitive and unsensitive circuits are grouped together to form a wiring harness or bundle. To minimize noise or other interference caused by external electromagnetic fields, a braided shield is formed around the entire wiring bundle. Typically, this braided shield is formed on site by threading the wiring bundle into a braiding machine, which has a plurality of spools. These spools each contain strands of the shielding material, such as plated copper. When the braiding machine is activated, the wiring bundle is fed into the machine, and the strands are woven into place, thereby forming a braided shield over the entire wiring bundle.
During assembly of the aircraft, the wiring bundle is routed throughout the aircraft to the various control systems and avionics. At each control system or avionics, a portion of the wires are branched off from the wiring bundle to connect with the corresponding component. However, the portion of wires connected to the corresponding component must also be shielded to prevent the occurrence of noise caused by external electromagnetic fields. Therefore, prior to the routing of the wiring bundle through the aircraft, the operator must first feed one leg of the wiring bundle through the braiding machine to form a braided shield along the wiring bundle. The operator must then manipulate the now shielded wiring bundle to feed the unshielded leg of the wiring bundle through the braiding machine. Accordingly, this method is inefficient and requires the operator to have enormous skill with the braiding machine to manipulate the various branches of the wiring bundle. Furthermore, if the wiring bundle needs to be exposed for any reason in the future, such as for service, the machine braided shield must be cut to expose the wires. This cutting of the machine braided shield destroys the shield, thereby introducing electromagnetic fields into the wiring bundle, unless the shield is laboriously repaired.
Accordingly, there exists a need in the relevant art to provide a method for conveniently and effectively shielding branched wiring bundles in an aircraft or the like from external electromagnetic field sources without the use of a braiding machine. Furthermore, there exists a need in the relevant art to provide a device for splitting the braided shield to form a shielded joint at the branching point. Still further, there exists a need in the relevant art to overcome the disadvantages of the prior art.